Some remarks on a new exotic spacetime for time travel by free fall

This work is essentially a review of a new spacetime model with closed causal curves, recently presented in another paper (Class. Quantum Grav. \textbf{35}(16) (2018), 165003). The spacetime at issue is topologically trivial, free of curvature singularities, and even time and space orientable. Besides summarizing previous results on causal geodesics, tidal accelerations and violations of the energy conditions, here redshift/blueshift effects and the Hawking-Ellis classification of the stress-energy tensor are examined.Comment: 17 pages, 9 figures. Submitted as a contribution to the proceedings of "DOMOSCHOOL - International Alpine School of Mathematics and Physics, Domodossola 2018". Possible text overlaps with my previous work arXiv:1803.08214, of which this is essentially a review. Additional results concerning redshift/blueshift effects and the classification of the stress-energy tensor are presented her

Idiopathic intracranial hypertension: the association between weight loss and the requirement for systemic treatment

<p>Abstract</p> <p>Background</p> <p>To determine whether weight loss is significantly associated with a discontinuation of treatment for idiopathic intracranial hypertension</p> <p>Methods</p> <p>The notes of 36 patients with idiopathic intracranial hypertension under regular review for at least 12 months by a single neuro-ophthalmologist were retrospectively reviewed. Weight was recorded at each assessment and weight loss recommended. Treatment was adjusted according to symptoms, visual function including visual fields and optic disc appearance only. Patients were divided according to duration of continuous follow-up, and then sub-divided as to whether they were on or not on treatment at most recent review and whether weight loss had been achieved compared to presentation. Survival analysis was performed to assess the probability of remaining on treatment having lost weight.</p> <p>Results</p> <p>Considering the patients as 3 groups, those with at least 12 months follow-up (n = 36), those with at least 18 months follow-up (n = 24) and those with 24 months or more follow-up (n = 19), only the group with 24 months or more follow-up demonstrated a significant association between weight loss and stopping systemic treatment (Fisher's exact test, p = 0.04). Survival analysis demonstrated that the probability of being on treatment at 5 years having gained weight was 0.63 and having lost weight was 0.38 (log rank test, p = 0.04). The results suggest that final absolute body mass index is more important than the change in body mass index for patients who stop treatment (Mann Whitney U, p = 0.05).</p> <p>Conclusion</p> <p>This is the first study to demonstrate that weight loss is associated with discontinuation of treatment. Unlike previous studies, our results suggest that final absolute body mass index is more important for stopping treatment than a proportional reduction in weight.</p

BRCA1 and BRCA2 mutations in a population-based study of male breast cancer

Background: The contribution of BRCA1 and BRCA2 to the incidence of male breast cancer (MBC) in the United Kingdom is not known, and the importance of these genes in the increased risk of female breast cancer associated with a family history of breast cancer in a male first-degree relative is unclear. Methods: We have carried out a population-based study of 94 MBC cases collected in the UK. We screened genomic DNA for mutations in BRCA1 and BRCA2 and used family history data from these cases to calculate the risk of breast cancer to female relatives of MBC cases. We also estimated the contribution of BRCA1 and BRCA2 to this risk. Results: Nineteen cases (20%) reported a first-degree relative with breast cancer, of whom seven also had an affected second-degree relative. The breast cancer risk in female first-degree relatives was 2.4 times (95% confidence interval [CI] = 1.4–4.0) the risk in the general population. No BRCA1 mutation carriers were identified and five cases were found to carry a mutation in BRCA2. Allowing for a mutation detection sensitivity frequency of 70%, the carrier frequency for BRCA2 mutations was 8% (95% CI = 3–19). All the mutation carriers had a family history of breast, ovarian, prostate or pancreatic cancer. However, BRCA2 accounted for only 15% of the excess familial risk of breast cancer in female first-degree relatives. Conclusion: These data suggest that other genes that confer an increased risk for both female and male breast cancer have yet to be found

Maximal Spontaneous Photon Emission and Energy Loss from Free Electrons

Free electron radiation such as Cerenkov, Smith--Purcell, and transition radiation can be greatly affected by structured optical environments, as has been demonstrated in a variety of polaritonic, photonic-crystal, and metamaterial systems. However, the amount of radiation that can ultimately be extracted from free electrons near an arbitrary material structure has remained elusive. Here we derive a fundamental upper limit to the spontaneous photon emission and energy loss of free electrons, regardless of geometry, which illuminates the effects of material properties and electron velocities. We obtain experimental evidence for our theory with quantitative measurements of Smith--Purcell radiation. Our framework allows us to make two predictions. One is a new regime of radiation operation---at subwavelength separations, slower (nonrelativistic) electrons can achieve stronger radiation than fast (relativistic) electrons. The second is a divergence of the emission probability in the limit of lossless materials. We further reveal that such divergences can be approached by coupling free electrons to photonic bound states in the continuum (BICs). Our findings suggest that compact and efficient free-electron radiation sources from microwaves to the soft X-ray regime may be achievable without requiring ultrahigh accelerating voltages.Comment: 7 pages, 4 figure

Dysembryoplastic neuroepithelial tumor and probable sudden unexplained death in epilepsy: a case report

<p>Abstract</p> <p>Introduction</p> <p>This is the first report of the case of a patient with a natural history of dysembryoplastic neuroepithelial tumor associated with probable sudden unexplained death in epilepsy. These tumors are benign, arising within the supratentorial cortex. Over 100 cases have been reported in the literature since the first description by Daumas-Duport in 1988.</p> <p>Case presentation</p> <p>A 24- year-old Caucasian woman had a long period of intractable complex partial seizures, sometimes with tonic-clonic generalization and neuropsychological abnormalities. Magnetic resonance imaging showed a cortico-subcortical parietal tumor with all the characteristics of these types of tumors. After 14 years of evolution, our patient died suddenly during sleep.</p> <p>Conclusion</p> <p>To the best of our knowledge, this is the first case of probable sudden unexplained death in symptomatic epilepsy due to dysembryoplastic neuroepithelial tumor with natural history. Early and complete excision, with functional studies before and during the surgery, leads to better control of seizures, avoiding neuropsychological changes and the risk of death. Patients with refractory epilepsy should be evaluated for any sleep disorders and should have complete cardiology assessments including electrocardiographic evaluation of cardiac rhythm disturbances.</p

Elucidating the aetiology of human Campylobacter coli infections

Peer reviewedPublisher PD

Non-syndromic Hearing Impairment in a Hungarian Family with the m.7510T>C Mutation of Mitochondrial tRNA^^Ser(UCN)^^^ and Review of Published Cases

The m.7510T>C mitochondrial DNA (mtDNA) mutation is a tRNA(Ser(UCN)) alteration leading to matrilineal isolated hearing impairment. The current paper reviews the available reports on the m.7510T>C mtDNA mutation, with special attention to phenotypic variations and haplogroup background. A Hungarian family, the fourth family reported in the literature, is presented, in which analysis of three generations with bilateral isolated hearing loss revealed the m.7510T>C tRNA(Ser(UCN)) mutation in homoplasmic form in the affected members. Haplogroup analysis verified an unnamed subgroup of mitochondrial haplogroup H. Previously reported Spanish and North American Caucasian families belong to different subgroups of haplogroup H. Analyzing our biobank of Hungarian patients with sensorineural hearing loss, we did not detect this mutation in any other patient, nor was it found in Caucasian haplogroup H control samples. Comparing the cases reported so far, there is interfamilial variablity in the age of onset, accompanying symptoms, and haplogroup background. Our case adds further genetic evidence for the pathogenicity of the m.7510T>C mutation and underlines the need to include full mtDNA sequencing in the screening for unexplained hearing loss

Individualization as driving force of clustering phenomena in humans

One of the most intriguing dynamics in biological systems is the emergence of clustering, the self-organization into separated agglomerations of individuals. Several theories have been developed to explain clustering in, for instance, multi-cellular organisms, ant colonies, bee hives, flocks of birds, schools of fish, and animal herds. A persistent puzzle, however, is clustering of opinions in human populations. The puzzle is particularly pressing if opinions vary continuously, such as the degree to which citizens are in favor of or against a vaccination program. Existing opinion formation models suggest that "monoculture" is unavoidable in the long run, unless subsets of the population are perfectly separated from each other. Yet, social diversity is a robust empirical phenomenon, although perfect separation is hardly possible in an increasingly connected world. Considering randomness did not overcome the theoretical shortcomings so far. Small perturbations of individual opinions trigger social influence cascades that inevitably lead to monoculture, while larger noise disrupts opinion clusters and results in rampant individualism without any social structure. Our solution of the puzzle builds on recent empirical research, combining the integrative tendencies of social influence with the disintegrative effects of individualization. A key element of the new computational model is an adaptive kind of noise. We conduct simulation experiments to demonstrate that with this kind of noise, a third phase besides individualism and monoculture becomes possible, characterized by the formation of metastable clusters with diversity between and consensus within clusters. When clusters are small, individualization tendencies are too weak to prohibit a fusion of clusters. When clusters grow too large, however, individualization increases in strength, which promotes their splitting.Comment: 12 pages, 4 figure

New mutations at the imprinted Gnas cluster show gene dosage effects of Gsα in postnatal growth and implicate XLαs in bone and fat metabolism, but not in suckling

The imprinted Gnas cluster is involved in obesity, energy metabolism, feeding behavior, and viability. Relative contribution of paternally expressed proteins XLαs, XLN1, and ALEX or a double dose of maternally expressed Gsα to phenotype has not been established. In this study, we have generated two new mutants (Ex1A-T-CON and Ex1A-T) at the Gnas cluster. Paternal inheritance of Ex1A-T-CON leads to loss of imprinting of Gsα, resulting in preweaning growth retardation followed by catch-up growth. Paternal inheritance of Ex1A-T leads to loss of imprinting of Gsα and loss of expression of XLαs and XLN1. These mice have severe preweaning growth retardation and incomplete catch-up growth. They are fully viable probably because suckling is unimpaired, unlike mutants in which the expression of all the known paternally expressed Gnasxl proteins (XLαs, XLN1 and ALEX) is compromised. We suggest that loss of ALEX is most likely responsible for the suckling defects previously observed. In adults, paternal inheritance of Ex1A-T results in an increased metabolic rate and reductions in fat mass, leptin, and bone mineral density attributable to loss of XLαs. This is, to our knowledge, the first report describing a role for XLαs in bone metabolism. We propose that XLαs is involved in the regulation of bone and adipocyte metabolism